1. Field of the Invention
The present invention relates to an electric drive device for a camera, for driving a movable mirror and a lens diaphragm by a motor and also charging a shutter.
2. Related Background Art
FIG. 3 shows the general arrangement of a conventional driving mechanism of a camera.
A sequence motor M1 for driving the movable mirror and the lens diaphragm, and charging the shutter, is provided in a winding spool. Mechanisms linked with said motor M1 are provided in an upper space S1 at the film winding side of the camera, and in a space S2 at the side of the mirror box.
A film feeding motor M2 is also provided for winding and rewinding the film. A mechanism linked with said motor M2 is provided in a bottom space S3 of the camera.
FIG. 4 is a perspective view showing the above-explained driving mechanism in more detail.
At first there will be explained a mirror-up operation conducted by the rotation of the sequence motor in a first direction.
In response to the depression of a shutter button, the sequence motor M1 rotates clockwise. The rotation is transmitted through reducing gears 51 - 55 to a charging cam gear 56, which is thereby rotated anticlockwise.
At the lower end of said gear 56 there is fixed a mirror driving pin 57, which is in contact with a mirror driving lever 58, and which rotates said lever to the right (clockwise). An end of said lever 58 is rotatably supported by a sequence base plate (not shown), while the other end engages with a mirror driving vertical lever 60, thereby rotating said lever 60 to the right by the rotation of the charging cam gear 56.
On an unrepresented (i.e., not illustrated) plate constituting the mirror box, the mirror driving vertical lever 60, a diaphragm return lever 61 and a diaphragm lever 62 are fitted on a common shaft, (not shown) and are biased toward the left (anticlockwise) by springs 63, 64, toward a position of contact with an initial position setting pin 65.
A movable mirror 66 is, in said initial state prior to shutter releasing, positioned in front of the film plane, with an angle of 45.degree. with respect to the photographing optical path.
Said movable mirror is rotatably supported by a rotary shaft at 67, and is biased clockwise by a mirror-down spring 68.
On a side of said mirror there is fixed a mirror driving pin 69, which protrudes in the moving trajectory of a lever 70 formed on an end of the mirror driving vertical lever 60.
The rotation of the mirror driving vertical lever 60 to the right in response to the shutter releasing operation pushes up said mirror driving pin 69, whereby the movable mirror 66 is lifted.
Also the diaphragm return lever 61 rotates clockwise together with said vertical lever 60. A diaphragm driving spring 74, provided between the diaphragm return lever 61 and the diaphragm lever 62, thus causes clockwise rotation of the diaphragm lever 62. An end 62a of said diaphragm lever 62 is in contact with a diaphragm lever of an unrepresented lens, so that the diaphragm aperture in said lens is gradually closed by the clockwise rotation of said diaphragm lever of the camera body.
Gear teeth provided on the other end 62b of the diaphragm lever 62 mesh, through an increasing gear 71, with a diaphragm controlling ratchet gear 72 and a diaphragm controlling encoder 73 to effect diaphragm control, in which the ratchet gear is stopped when an output corresponding to the preset diaphragm aperture value is obtained from the encoder.
The mirror-up operation is completed when the mirror driving pin 57 reaches an upper dead point with respect to the mirror driving lever 58 by anticlockwise rotation of the charging cam gear 56 by 90.degree., whereupon the sequence motor M1 is stopped.
Subsequently a mirror-down operation is initiated by the rotation of the sequence motor in a second direction. The reverse rotation of said sequence motor M1 is started upon detection of completion of shutter curtain movement corresponding to a predetermined shutter speed.
The clockwise rotation of the charging cam gear 56 moves the mirror driving lever 58 to the left, causes the descent of the movable mirror and the return of the diaphragm lever 62 to an open aperture position. Also in the course of said mirror-down operation, an unrepresented shutter is charged by a rotating shaft driven by bevel gears 56a, 59 through on the charging cam gear 56.
Subsequently the film feeding motor M2 is activated to advance the film, in order to prepare for the next phototaking operation.
In the conventional structure explained above, the mechanism for sequential control is divided into three parts, namely a part including the sequence motor M1 to the mirror driving cam (51 - 56, 58 etc.), another part providing the mirror driving mechanism (60, 69, 70 etc.), and still another part including the shutter charging cam drive (59 etc.) and a shutter charging control unit (not shown), are of which are accommodated in the spaces S1 and S2. As a result such conventional structure presents the following drawbacks:
1. An increased number of component parts, involving complicated mechanisms leading to poor assembling efficiency and increased cost;
2. Divided structures requiring a larger space, thus enlarging the dimensions of the camera itself; and
3. Direction of motors different from the final driving direction, requiring changes in direction and leading to a reduced efficiency.
In addition, motors of large power, which are not only bulky but also expensive, have been required.